
public class Solution {
    public int findTargetSumWays(int[] nums, int target) {
        // sum(P) - sum(N) = target
        // sum(P) + sum(N) + sum(P) - sum(N) = target + sum(P) + sum(N)
        // sum(P) = (target + sum)/2
        int sum = 0;
        for (int num : nums) {
            sum += num;
        }
        if (sum < target || (sum + target) % 2 == 1) {
            return 0;
        }
        target = (target + sum) / 2;
        int[] dp = new int[target + 1];
        dp[0] = 1;

        for (int i = 0; i < nums.length; i++) {
            for (int j = target; j >= nums[i]; j--) {
                dp[j] += dp[j - nums[i]];
            }
        }
        return dp[target];
    }
}
